1. Field of the Invention
This invention relates generally to connectors used with optical components. More particularly, it relates to connectors which may be sealed to components by fusing.
2. General Background and Related Art
For joining optical components together, or for incorporation of optical components into other devices, it is often desirable to make use of a ferrule. A ferrule is a piece of glass, ceramic, plastic or metal material having one or more holes into which components such as optical fibers may be inserted. Ferrules offer additional structural strength and support to the fiber as well as facilitating alignment of a fiber with another component.
In addition to optical applications, ferrules may find uses in applications such as joining of capillaries or other components.
In many cases it is desirable to provide a seal to prevent migration of oxygen or other contamination from the environment into a package intended to isolate an active device such as a semiconductor laser or photodetector. In other cases, a fiber must pass through a bulkhead, for example on a mobile platform or in a chemical reactor. A ferrule may also act as a heat sink or power block when a fiber is used in a high power coupling application such as a medical laser delivery system. In other cases, it is important to minimize stress induced by thermal expansion mismatches between the ferrule, bonding adhesive, and inserted optical fiber. The stresses generated by the expansion mismatch can degrade optical and mechanical performance of the overall package. Likewise, ferrules are employed in the construction of modular components which must be conveniently connected and disconnected while maintaining good alignment between fibers and other components.
It has been known in the art to seal fibers to ferrules by several methods including epoxies, metalization of the fiber or by swaging material around the fiber. Some attempts have been made to seal fibers by fusing the fiber together with the ferrule. These have had limited success as the seal generally fails to hold, or the fiber and/or the ferrule fails, particularly when fiber and ferrule are of differing materials. Even if each is made of glass, for example, fusing tends to distort the fiber to such an extent that the fiber's optical characteristics are changed. In the case of single mode or polarization maintaining fibers, the fiber geometry is crucial to its proper operation. Likewise, the small diameter of both core and cladding, and in the case of polarization maintaining fibers, the precise stress distributions, are extremely difficult to maintain during a fusing operation. Moreover, fusing tends to produce stress within the structure of the fiber and the ferrule which may lead to premature failure.